Method of dispersing fillers in ethylene/alpha-olefin



United States Patent 3,394,100 METHOD OF DISPERSIN G FILLERS INETHYLENE/ALPHA-OLEFIN Luigi Falcone and Luigi Torti, Ferrara, Italy,assignors to Montecatini Edison S.p.A., Milan, Italy, a corporation ofItaly No Drawing. Filed July 24, 1962, Ser. No. 212,112 Claims priority,apgilicatizon6 Italy, July 27, 1961,

Claims ((1 260--4l) ABSTRACT OF THE DISCLOSURE The present inventionrelates to a process for preparing vulcanized products having improvedmechanical properties and a high electric resistivity from saturatedamorphous copolymers of ethylene with alpha-olefins, e.g., propylene orbutene, in the presence, if desired, of a compound capable ofneutralizing the acidity of fillers and/ or vulcanization acceleratorswhich are present,

Saturated amorphous copolymers of ethylene with alpha-olefins exhibitall the properties of substances generally known as rubber, but theydiffer from unsaturated rubbery products in so far as vulcanization isconcerned, since such saturated copolymers cannot be crosslinked bytraditional ingredients, namely sulfur and accelerators.

These copolymers, on the contrary, can be vulcanized by vulcanizationmethods involving the use of organic peroxides in the presence of smallamounts of sulfur.

Saturated copolymers of ethylene with alpha-olefins exhibit veryvaluable characteristics, some of which depend on their parafiinicnature. The vulcanized products offer very good resistance to thermalaging and to weathering, exhibit very good stability with respect toozone, and show a good resistance to light. Such products also haveexcellent electric properties as measured by insulation constant,dielectric constant, and dielectric losses.

A characteristic of such amorphous copolymers of ethylene withalpha-olefins is that they do not crystallize under stretching.Accordingly, vulcanized products having high tensile strength can beobtained only in the presence of reinforcing fillers.

It is therefore necessary to prepare a mix containing copolymer and afiller having a good processability, which mix is capable of producingan elastic reinforced vulcanized product having a high insulatingcapacity. Such vulcanized products can be used, for example, asdielectric materials for the insulation of metallic conductors.

From the point of view of electric insulation, some mineral fillers areparticularly advantageous due to their intrinsic electric properties,the desirable processability they impart to the mix and, in some cases,the economic advantages they offer. Such fillers include oxides; e.g.,iron,

aluminum, silicon or titanium oxides; hydroxides, e.g., aluminum orsilicon hydroxides; carbonates, e.g., calcium, barium, zinc or magnesiumcarbonates; silicates, e.g., zinc, calcium, magnesium or aluminumsilicates; lithopone; and barium sulfate.

It has been observed that with respect to certain of the aforementionedfillers, more particularly those known as acid fillers such as somekaolins and silicas, vulcanization with organic peroxides is severelyimpaired by the negative influence on the peroxide which is exerted bythe filler. Therefore, recourse must be had to the use of particulartypes of organic peroxides not influenced by such fillers, or to theaddition of substances which neutralize the influence of the filler onthe peroxide. Suitable neutralizers include nitrogen-containingquinone-type compounds (pbenzoquinone dioxime,O-O-dibenzoyl-p-benzoquinonedioxime, p-nitrosophenol) together withperoxide and sulfur, or certain basic organic and/ or inorganicingredients which can be incorporated with the filler-p0lymer mix atappropriate elevated temperatures.

The vulcanized products thus obtained however are inadequatelyreinforced, (i.e., will exhibit a rather low elastic modulus and tensilestrength in certain applications), do not vulcanize in the presence ofsteam, and generally exhibit low values for electric resistivity.

When a good dispersion of the filler in the mix is obtained, there is animprovement in the mechanical properties but not in the electriccharacteristics.

It is an object of the present invention to obtain homogeneous mixesfrom which vulcanized products having both high mechanical andelectrical properties can be obtained.

In accordance with one aspect of our invention, the aforementionedcopolymer is homogeneously mixed with a white mineral filler and adispersion. promoter, along with, if desired, a neutralizer for thefiller acidity, and the mix thus obtained is subjected to atherrno-rnechanical treatment, then cooled and, after addition ofvulcanizing agents, is vulcanized, thereby obtaining a vulcanizedarticle having high mechanical properties and a high electricresistivity.

It has surprisingly been found that vulcanized articles with optimummechanical and electric characteristics can be obtained only bycontemporaneously observing three specific precautions, namely: i

(a) The choice of a suitable filler (white mineral (b) Mixing thisfiller with the copolymer and a dispersion promoter,

(c) Thermo-mechanical treatment of these components in the absence ofvulcanizing agents.

The addition of small amounts of dispersion promoter to a mix containingthe copolymer, the mineral filler, and also the vulcanizing ingredients(sulfur and peroxide) results in a vulcanized product having goodelastic properties and good reinforcing characteristics. Thisimprovement in the elastic and mechanical properties of the vulcanizedproducts is to be contrasted with the electric insulationcharacteristics which are in fact only slightly higher than thoseobtainable by processes known heretofore. Accordingly, to obtain thebenefits of our invention, the vulcanizing ingredients must not be addeduntil after the copolymer, filler, and dispersion promoter have beensubjected to therrno-mechanical treatment.

Moreover, it has been observed that by carrying out the vulcanization inthe presence of steam, there occurs a worsening in the characteristicsof the final vulcanized products with the results being similar to thosenormally obtained in the absence of a dispersion promoter, e.g., maleicanhydride. These experiments lead us to conclude that reinforcing action(mechanical characteristic) and dispersion of the filler (electricproperties) are not necessarily related to one another.

Usually a good dispersion of the filler can be obtained in an internalmixer at a sufiiciently high temperature. However, it has been observedthat such dispersion is not stable and that the filler tends tofiocculate in the subsequent heating during vulcanization. In theproduction of insulating sheaths for electric cables there has oftenbeen observed a considerable decrease in insulating properties ascompared with those of the crude starting product. A method of obtaininga good dispersion of white fillers comprises incorporating in the mixes,in addition to the vulcanizing agents, also from about 1 to of a zinc orlead soap of a fatty acid with more than 5 carbon atoms. Goodcharacteristics are Obtained, but vulcanization in the presence of acidfillers may be deleteriously affected as shown by poor mechanicalcharacteristics of the vulcanized products.

By preparing the filler-polymer mix by the process of the presentinvention in the presence of a dispersion promoter in an internal mixerand subjecting the mix to a thermo-rnechanical treatment at atemperature of from about 200 to 300 C., there is no difference betweenthe insulating characteristics of the crude mix and those of thevulcanized mix.

It is as though in the presence of the dispersion promoter, when themixes are subjected to a thermal pretreatment at 200-300 C., thedispersion of the filler becomes irreversible.

Moreover, the process is also applicable to extruded products vulcanizedin steam, since both electric and mechanical characteristics of thevulcanized products are not influenced by the vulcanization, even ifcarried out with this technique.

The copolymer used in the process of the invention should desirably havea content of at least mole percent ethylene and a molecular weight offrom about 40,000 to 600,000, and preferably from about 60,000 to300,000. The white mineral filler is desirably an alkaline-earth metalcarbonate or sulfate, or silica, or natural or artificial complexsilicates, and preferably is a kaolin, clay, talc, calcium carbonate,silica or barium sulfate. According to a particular feature of theinvention, the dispersion promoter is selected from the group consistingof:

(1) Saturated or unsaturated aliphatic dicarboxylic acids containingless than five crabon atoms in the principal chain (including tartaricacid);

(2) Anhydrides, esters or salts of such acids;

(3) Saturated or unsaturated aliphatic monocarboxylic acids containingless than four carbon atoms in the principal chain;

(4) anhydrides, esters, or salts of said acids;

(5) Furfural, furfuryl alcohol, furoic acid, and derivatives thereof.

Such promoters may be introduced as such into the mixtures as forexample in the case of maleic acid, fumaric acid, maleic anhydride,succinic acid, malonic acid, oxalic acid, acetic acid, formic acid,acetic anhydride, ethyl acrylate, diethyl malonate, basic lead maleateand the like; or in the form of their precursors or of compounds whichthrough the effect of the temperature corresponding to the thermalpretreatment and/or in the presence of the used mineral fillers, may,for example by dehydration, decarboxylation and the like, form productsbelonging to the class described; this is, for example, the case ofcitric acid, aconitic acid, malic acid, tricarballylic acid,trioxymethylene, etc.

The amount of promoter added to the mix is desirably 4 from about 0.1 to15 parts, and preferably from about 0.2 to 10 parts by weight per partsof filler.

The thermal treatment is desirably carried out at from about 200300 C.contemporaneously with a mechanical homogenization in a roll mixer or ina Banbury mixer.

After this critical treatment, sulfur and peroxide (vulcanizing agents)are added to the mix (0.3 to 1.5 gram atom of sulfur, and preferably 1gram atom of sulfur, per mole of peroxide, and 0.1 to 10 parts by weightof peroxide per 100 parts of polymer).

The vulcanization is then desirably carried out at a temperature of fromabout to 220 C., and preferably from about to C.

Finally it has also been observed that, in order to obtain greatercross-linking, the organic peroxide can conveniently be protectedagainst the action of the acid additive by the addition of small amountsof a metal oxide (e.g., MgO, ZnO, CaO, PbO, etc.).

Of course, when the peroxide is of a type which is particularlysensitive to the action of acids, such as dicumyl peroxide, the amountof metal oxide to be added will be considerably higher than the amountneeded with peroxides which are not very sensitive to acids, such astetrachlorinated di-tertiary-butylperoxide.

The invention will now be described with reference to the followingillustrative examples.

EXAMPLE 1 In a 50-litcr internal mixer a mix M having the followingcomposition is prepared:

Parts by weight Copolymer 100 Calcined kaolin 100 An ethylene-propylenecopolymer containing 50 moles of ethylene and 50 moles of propylene andhaving a Mooney viscosity ML (1+4, 100 C.) of 45 is used. (Equivalentresults may be obtained using an ethylenebutene copolymer containing 50moles of ethylene and 50 moles of butene and having a similar Mooneyviscosity.)

In a roll mixer a mix consisting of the following components isprepared:

Parts by weight The mix M 200 ZnO 2 Maleic anhydride 5 The mix issubjected to a thermo-mechanical treatment (warm mastication) for 10minutes at 230 C.

After this treatment the mixture is left to cool and is admixed in thecold in a roll mixer with thevulcanization agents consisting of peroxideand sulfur, thus obtaining a complete mix having the followingcomposition:

Parts by weight t. calcined kaolin MIX M copolymer 100 ZnO 2 Maleicanhydride 5 Tetrachlorinated di-tertiary-butylperoxide 3.4 Sulfur 0.4

megohm kilometers (Mt2km.), defined by the following formula RXL log 3X1000 in which R==resistance in megohms L=length of the cable pieces inmeters d=diameter of the conductor D=outer diameter of the cable (2)Discs having a thickness of 0.7 mm. and a diameter of 300 mm. vulcanizedin a press at 165 C. for 50 minutes, on which the following values weredetermined according to ASTM D14959.

Maximum voltage tolerated (kv.) Max. electric field tolerated kv./mm.

Tensile strength kg./cm. 63 Elongation at break percent 390 Modulus at300% kg./cm. 60 Residual elongation percent 8.5 Tear resistance kg./cm36 Control test (a) In a -1iter internal mixer there was prepared theabove mix M. From this mix a unipolar cable was manufactured as in (1).Several pieces of crude cable, with a length of 10 cm., were conditionedin water at C. for 48 hours. The insulation constant Ki (average ofvarious measurements) was 5,000 Mtlkm.

(b) The :above pieces of crude cable were subjected to a thermaltreatment at 170 C. for 30 minutes and were then conditioned in water at60 C. for 48 hours. The insulation constant Ki was 0.01 Mtlkrn; thisshowed the existence of a destructive effect of the temperature upon theresistivity of the mix.

(c) A mix having the following composition was prepared:

Parts =Mix M 1 200 ZnO 1 :l Diphenylguanidine 1 Sulfur 0.4Tetrachlorinated di-tertiary-butylperoxide 3.4

1 Mzmlx of Example 1.

The metal oxide and the organic base, corrective agents normally used inthe vulcanization of mixes containing acid fillers, were added in a rollmixer. The vulcanizing agents (peroxide and sulfur) were alsoincorporated in a 0.7 mm. and a diameter of 300 mm. (similar to thosereported in 2) were molded in a press at for 50 minutes. Themeasurements carried out according to ASTM D-l49-59 gave the followingresults:

Max. voltage tolerated kv.... 11 Max. electric field tolerated kv./mm12.5

(3) Again with the same mix, small discs similar to those reported in(3), (diameter 52.5 mm., thickness 2 mm.) were molded in a press at 165for 50 minutes and then subjected to the absorption test described in(3). After 7 days in the bath, the specimens were removed, dried andweighed, showing a water absorption of 6 mg./cm.

(d) A mix having the following composition was prepared:

Parts Mix M 1 200 ZnO 10 Stearic acid 5 Sulfur 0.4 Tetrachlorinateddi-tertiary-butylperoxide 3.4

1 Mix M of Example 1.

With this mix 500 m. of electric cable was made under the conditionsreported in (l). The insulation constant was 1000 Mtzkm.

There is an improvement, as compared with (c) resulting from thepresence of a dispersant such as stearic acid.

(2") The tests carried out on discs having a thickness of 0.7 mm. and adiameter of 300 mm. obtained from the preceding mix, as reported in (2)and (2) gave the following results:

Max. voltage tolerated kv 25 Max. electric field tolerated kv./mm- 29.9

(3) The tests carried out on discs having a thickness of 2 mm. and adiameter of 52.5 mm., obtained from the above mix as described in (3)and (3), showed a water absorption of 3 mg./cm.

(e) A mix having the following composition was prepared:

Parts Mix M 200 ZnO 2 Maleic anhydride 5 Sulfur 0.4 Tetrachlorinatedditertiary-butylperoxide 3.4

1 Mix M according to Example 1.

This mix was prepared in a roll mixer. The insulation constant,determined on a cable as described in (1), is 400 Mtlkm. This valuehowever has a low reproducibility. This shows that by replacing stearicacid with maleic anhydride (a promoter according to the invention) butin the absence of thermal treatment, the desired improve ments are notobtained.

EXAMPLE 2 With the same formulations of Example 1, the following mixeswere prepared for determining the relative mechanical characteristics:

Mixes A, B, C, D and B were prepared in a roll mixer. The mix E wassubjected to the thermal treatment according to the invention asreported in Example 1, Le, before the addition of the vulcanizationagents.

7 Mixes A, B, C, D and E were vulcanized in a press and in steam at thetemperature (165 C.) and for the same time (50 minutes).

Mechanical tests carried out according to ASTM D 412-51 gave thefollowing results:

The Mooney viscosity of the crude IlllX is only 25. This assures goodworkability, even with reduced amounts of filler, which make it possibleto obtain very high electric insulation values.

The preceding examples were intended mainly to il- TABLE 2 A B D E PressSteam Steaiu Press Steam Press Steam Press Steam Tensile strength,kg./crn.- 30 43 30 33 30 70 40 75 (i Elongation at break, Percent 1, 1'01 000 700 75.0 800 450 550 400 500 Modulus at 300%, lag/cm. i7 it 20 it14 (i0 23 70 58 Residual elongation, Percent 250 Lo 2O 9 1| 10 Tearstrength, kg/cm 23 a 40 22 42 After elongation at 200% for 1 hour andreading after 1 minute.

EXAMPLE 3 Parts Ethylene-propylene copolyinier (:50 molar ratio),

Mooney viscosity ML (1+4, 100 C.):20 100 Calcined kaolin 5O ZnO 2 Maleicanhy-dride 5 lustrate the improved electrical characteristics of thevulcanized products obtained according to the present invention.

Further examples are reported hereinbelow to illustrate an the favorableeffects upon mechanical characteristics (reinforcing) and shows otherformulations within the scope of the invention, and particularly showsthe importance of the thermal pretreatment in the preparation of themixes before incorporating the vulcanizing agents. The

2;, effect of varying the amount of promoter having an acid character isalso shown.

EXAMPLE 4 This example shows the effect of the amount of pro- 30 moter(maleic anhydride) upon the characteristics of the vulcanized productsin absence of thermal pretreatrent. The results are shown in Table 3.

TABLE 3 Ethylene-propylene copolynier (50:50

molar ratio) 100 100 100 100 100 100 100 Cale-tried kaolin 100 100 100100 100 100 100 2 2 2 2 2 2 2 Snlfuiu. 0 4 0.4 0 4 0.4 0.4 0 4 0 4Tetraehlonnated ditertiarybutylperoxide 3. 4 3. 4 3. 4 3. 4 3. 4 3. 4 3.4 Maleic anhydride 0. 5 1 3 5 7 10 Tensile strength, kg./ein.- 54 56 b371 78 71 47 Elongation at break, percent" 600 650 580 400 450 410 560Modulus at 300%, kg./em. 31 42 50 66 (i0 40 Residual elongation,percent" 12. 5 9 l0 9. 5 10 18 28 Tear resistance, kg./crn 20 29 36 3736 34 32 sheath'=5 mm.) was then extruded and vulcanized con- EXAMPLE 5tinuously with saturated steam at 12 atmospheres at the rate of 50 m./minute.

This cable was subjected to various tests in order to This example showsthe effect of the amount of metal oxide (ZnO) upon cross-linking in thepresence of maleic anhydride, in the absence of thermal pretreatment.

Mix No 1 2 3 4 5 Copolymer 100 100 100 100 Calcined kaolin 100 100 100100 100 Maleic anhydride 5 5 5 5 5 Tetrachlorinatedditertiaryl)utylperoxidm 3.4 3.4 3 4 3.4 3 4 Sulfur 0. 4 0. 4 0 4 0. 4 04 Z 0 1 2 3 4 Mechanical characteristic Tensile strength, kg/crn? 56 (SS78 66 61 Elongation at break, percent 580 450 440 470 490 Modulus at300%, kg./em. 46 59 66 60 55 Residual elongation, percent 14 9. 5 9 8. 58. 5 Tear strength, kgJcnr 40 34 39 32 30 determine the insulationconstant, the dielectric rigidity EXAMPLE 6 and the water absorption.

Dielectric constant Ki MQkm. 100,000 Dielectric rigidity kv./rnn1 40,000Water absorption "mg/cm?" 3 The relative mechanical characteristics,determined on specimens prepared from products vulcanized in a press atC. for 50 minutes were as follows:

Tensile strength "kg/cm?" 55 Elongation at break "percent" 550 Modulusat 300% kg./cm. 30 Residual elongation percent 8 Tear resistance "kg/cm.25

This example shows the effect of variations in the amount of maleicacid, used as promoter, on the characteristics of the vulcanizedproducts, without thermal pretreatment.

Mix No 1 2 3 Ethylene-propylene copolymer 100 100 100 Caleinerl kaolin'letrachlorinate 3 4 3 4 3 4 O 2 2 Products vulcanized in a press at 165C. for 50 minutes-mechanical characteristics:

Tensile strength, kg./cm. 48 50 57 Elongation at break, peree Modulus at300%, lrg./em.

9 EXAMPLE 7 teristics and the insulation constant are reported in thefollowing table. Articles obtained from mixtures consisting of copoly-EXAMPLE 8 mer and calcinated clay which had been pretreated ther- Theresults of the measurements made on articles vulmally at 200 C. duringminutes in the presence of 5 canized at 165 C. for 50 minutes andobtained with a naleic acid promoter with diiferent white fillers, arere- Without promoter and Ethyl- Formic Oxalic Malonie Sueeinic MalicTartaric Maleie Furnarie Itaconie Citric without acrylate acid acld acidacid acid acid acid acid acid acid thermal treatment Composition:

Ethylene-propylene eopolymer 100 100 100 100 100 100 100 100 100 100 100100 Whitetex 100 100 100 100 100 100 100 100 100 100 100 100 Promotei 51.98 6.1 4 5 5 6.3 7.13 5 5 6 2 10 ZnO, 2 2 2 2 2 2 2 2 2 2 2 2 Sulphur0. 4 0. 4 0. 4 0- 4 0. 4 0. 4 0.4 0.4 0.4 0.4 0.4 0.4

'Ietrachlorinated diteitf 0 8.5 {11 11 8.5 9 10.5 10 10 12 Tearstrength, 42:1:1 33 38 34 40 44 46 44 41 Isolation eonstant 0.001 3, 550300 150 728 446 1,000 800 4,800 228 2, 470 1, 000

Diethyl Diethyl Furiurol Furiurylic Basie lead Acetic Trioxy- FuroieZine malonate malonate maleate anhydride methylene acid maleate Comosition:

lil thylene-propylene copolymer 100 100 100 100 100 100 100 100 hitetex100 100 100 100 100 100 100 100 7 5 5 5 4. 5 4 5 7. 5 2 2 2 2 2 2 2 20.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 Tensile strength, kg./cm. 60 70 78 j=150 50 3:2 39 1 Elongation at break, percent 1 600 400 35 5 430 520 640300 Elongation modulus at 300%, kgJcm. 43 63 51 51 42 28 Elongationmodulus at 100%, Ira/cm. 2 Residual elongation at 200%.... 10 9 7. 5 129. 5 9 12.5 8. 5 Tear strength, kg./em 27 35 33 38 31 31 25 42Insulation constant 2, 000 1, 900 1, 000 800 10 1, 000 10 100 4, 000

various promoters, have been prepared by vulcanization 45 ported in thefollowing table. The influence of thermal at 165 C. during 50 minutes.Both mechanical characpretreatment at 200 C. for 15 minutes on themechanical and electrical characteristics is shown.

Fixed components: Ethylene-propy1ene copolymer (50:50 molar), 100 parts;ML (1+4) 100 C., 45; Sulfur, 0.4; Tetraehlorinated ditertiary butylperoxide,

3.4 vulcanization time, 50; vulcanization temperature, 165 0.

Filler (parts per Thermal Tensile Elonga- Modulus Residual Tear ISO 100parts Promoter Treat- Strength, tion at at 300%, elongation, Resistance,hard- M.L. Garvey Kl of copolymer) ment kgJem. break, kg./em. percentkg./em. ncss Die percent Durosil 40 Maleg: acid 4, 200 0.; 15C..- 92 60046 10. 5 40 51 75 i 5 56, 600

Zn 2. Do do 113 810 24 16.5 28 5 90 8.5 0.001 A sil 40 M%leie acid 5,200 0.; 15!... 156 580 57 20 51 20,000

177 900 22 35 47 72. 5 12. 5 0. 001 140 500 18 45 1 1 18,300 186 900 2032. 5 62 12 0. 001 64 430 58 10 40 57 60 13. 5 10, 224 40 680 30 11 2564 100 13. 5 0. 001 47 410 47 12 45 60 50 9 5, 308 44 080 28 18 31 66 725 0. 001 200 0.; 15.... 540 58 9. 5 42 52 55 10. 5 5, 000 Do "do- 41 66025 14 22 68. 5 78 9 0 001 Whitctex 70, Maleic acid 5, 200 C.; 152... 75410 69 9 42 57 67 12 15, 000

Durosil 20 2110 2.

Do do 52 510 45 10 32 63 96 9. 5 0, 001 Do 200 0.; 15 75 580 56 14 4755.5 66 13. 5 14,978 Do 1 87 800 35 16. 5 34 68 111 10.5 0. 001 Whitetex70, Socal 200 0.; 15 67 370 64 10 42 57 55 10. 5 6,000

p0 42 520 37 12. 5 2s 63 on s. 5 o. 001 Whitetex 70, BaSOq .1. -do 2000.; 15C... 72 440 65 10 44 54 55 11.5 7,328

Do .do 46 460 43 12. 5 29 07 7. 5 0.001 Whltetcx 70, Lithodo 200 (1.;l5.. 70 400 61 10 44 54 55 11. 5 7, 286

one 50. p Do do- 43 530 37 11 29 65 82 9. 5 0. 001 Durosil, Hydratedsilic acid; Cab-O-Sil, S1614 pyrolysis silica; Soeal, ML indicates theMooney viscosity ML (1+4) at C. CaC0 Whitetex, washed and ealcinatedclay; Aerosil, S1014 pyrolysis Garvey Die: see Ind. Eng. Chemistry, Vol.34, No. 11, November silica; Lithopone, ZnS-BaSO (30-70). 1942, page1309.

The ISO hardness is measured according to ASTM standard D 1415-Variations can, of course, be made without departing from the spirit ofour invention.

Having thus described our invention, what we desire to secure and herebyclaim by Letters Patent is:

1. A process for preparing a vulcanized product having high mechanicalcharacteristics and a high electric resistivity, said process comprisingmixing a saturated amorphous copolymer selected from the groupconsisting of ethylenepropylene and ethylene-butene copolymerscontaining at least 35 mole percent of ethylene and having a molecularweight of from about 40,000 to 600,000, with a white mineral fillerselected from the group consisting of alkaline earth metal carbonates,alkaline earth metal sulfates, silica, and alkaline earth metalsilicates, and with a dispersion promoter selected from the groupconsisting of aliphatic dicarboxylic acids containing less than carbonatoms in the aliphatic chain which includes both carboxyl carbon atomsand a total of up to about carbon atoms, anhydrides, esters and salts ofsuch acids, aliphatic monocarboxylic acids containing less than 4 carbonatoms in the aliphatic chain which includes the carboxyl carbon atom anda total of up to about 9 carbon atoms, anhydrides, esters and salts ofsuch acids, furfural, :furfuryl alcohol, furoic acid, tartaric acid,citric acid, aconitic acid, malic acid, tricarballylic acid andtrioxymethylene, to thereby form a homogeneous mixture, masticating saidmixture at a temperature of from about 200 to 300 C., cooling, addingsulfur and an organic peroxide thereto, and vulcanizing at a temperatureof from about 110 to 200 C., to thereby obtain a product having highmechanical properties and a high electric resistivity.

2. The process of claim 1 wherein the initial mixing is carried out inthe presence of a metal oxide ucutralizer for said filler.

3. The process of claim 1, wherein the amount of dispersion promoter isfrom about 0.1 to 15 parts by weight per parts of filler.

4. The process of claim 1 wherein the amount of promoter is from about0.2 to 10 parts by weight per 100 parts of filler.

5. The process of claim 1, wherein said mastication is carried out withmechanical homogenization in a mixer.

6. The process of claim 1, wherein the sulfur is added in an amount offrom about 0.3 to 1.5 g atom per mole of peroxide.

7. The process of claim 6, wherein the sulfur and the peroxide are addedin equimolar amounts.

8. The process of claim 1, wherein the amount of peroxide is from about0.1 to 10 parts by weight per 100 parts of polymer.

9. The process of claim 1 wherein the vulcanization is carried out at atemperature of from about to 180 C.

10. The method of claim 1 wherein there is employed from about 50 toparts of said filler per 100 parts of copolymer.

References Cited UNITED STATES PATENTS 3,173,903 3/1965 Lukach et a1.260-882 2,655,492 lO/l953 Young et al. 2604l 2,692,870 10/1954 Pechukas260-78 3,012,016 12/1961 Kirk et al 2604l FOREIGN PATENTS 231,04810/1960 Australia.

JULIUS FROME, Primary Examiner.

I. H. DERRINGTON, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,394,100 July 23, 1968 Luigi Falcone et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Columns 7 and 8, the table for Example 5, first column, last linethereof, "Tear strength, kg./cm. should read Tear strength, kg./cm.Column 9, line 4, "calcinated" should read calcined Columns 9 and 10,the second half of the table for Example 7, the heading for the firstcolumn thereof, "Diethyl malonate" should read Cinnamic acid same table,the heading to the third column thereof,

"Furfurol" should read Furfural same table, the heading to the fourthcolumn thereof, "Furfurylic" should read Furfuryl alcohol same columns,the table for Example 8, the heading for the next to the last columnthereof, "Garvey Die" should read Swell-at Garvey Die Column 11, line30, "110 to 200 C." should read 110 to 220 C.

Signed and sealed this 13th day of January 1970.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents

